The thermal and photochemical degradation of nylon 66 in different
atmospheres is compared in Figure 1.2 by the percentage change in viscosity
number. Figure shows two interesting features. Compared to the control samples all
the post-heated samples in nitrogen and steam display a more rapid decrease in
viscosity number except for samples 5, 6, and 9. Of the two post-thermal
treatments, the effect of steam is quite dramatic in the case of sample 2, for which a
rapid change in viscosity number is observed that is certainly associated with a
higher concentration of degradation products generated in the polymer.